I emailed NRMP about this. Here is what they sent back...
***Applicants also may rank their preliminary programs after their main
program choices on the primary list if they wish to have those programs
considered as a stand alone program in case they do not match to any of
their advanced programs. This increases their chances of at least matching
to their first year of training but they will still need to scramble for an
advanced year program. Applicants who rank preliminary programs on their
primary rank order lists must consider that if matched to a preliminary
program only they will only be able to scramble for advanced programs
(which start a year later) and not to categorical programs that start in
the year of the match. It is a violation of the Match Participation
Agreement for the applicant to take another position in the scramble that
prevents them from starting the preliminary program to which they matched.
***For those applicants who do not want to be locked into this scenario and
prefer to be able to try for a variety of programs in the scramble, the
ranking of preliminary programs on the primary list as a safety net may not
be the best choice. Applicants are obligated to honor the matched
preliminary year program just as any other and so should weigh the benefits
of both methods.
